This could be an allergic recation, an insect bit or a skin
lesion. You would need to consult your doctor or skin
specialist to find out the cause and management.
You should take some oral antihistamine or antiallergic medications and see if it helps in your case. Apply calamine lotion to help soothe the itching. Do not apply any other creams or products , till you consult your doctor.
Also, keep the area clean.